Currently the major impediment to safe and effective laser angioplasty is the high incidence of arterial perforation. The aim of this research project is to evaluate the hypothesis that fiberoptic fluorimetry can distinguish atherosclerotic from normal artery and thereby guide the delivery of laser energy for plaque ablation. Preliminary investigation has shown that characteristic fluorescence can be induced in human atheromas by low power laser radiation. A fiberoptic catheter could there transmit low power radiation forfluorescence analysis and if correctly targeted, subsequently transmit high power laser radiation for plaque ablation. This proposal will evaluate fiberoptic fluorimetry of normal and atherosclerotic human cadaveric aorta, iliofemoral and coronary arteries using a helium cadmium laser (wavelength 325 nm) for fluorescence induction, and a microcomputer based optical multichannel analyzer for fluorescence analysis. The specific aims are to: 1) derive a discriminant function to differentiate atherosclerotic from normal arterial tissue histology based on laser-induced fluorescence characteristics; 2) evaluate fiberoptic laser-induce fluorescence spectroscopy in a fluid environment (saline, blood, or Fluosol); 3) evaluate the arterial fluorescence changes as plaque ablation proceeds using fiberoptic fluorimetry in conjunction with high peak power pulsed Alexandrite laser ablation (wavelength 378 nm frequency doubled); 4) evaluate whether exogenously administered fluorescent compounds (tetracycline hematoporphyrin derivative, or histologic dyes) localize to atherosclerotic plaque and enhance the diagnostic capabilities of fiberoptic fluorimetry; 5) evaluate the ability of computerized fiberoptic fluorimetry guidance to achieve selective plaque ablation without damage to the underlying arterial wall in an in vitro laser angioplasty model. It is hoped that the currently high risk of arterial perforation during laser angioplasty can be eliminated by fiberoptic fluorimetry guidance. In addition, fluorimetry guided laser ablation may have broad application in other areas of medicine by the potential to achieve selective tissue ablation of any mass that is distinguishable by fluorescence properties.